The use of cannulation in the medical arts is well known. Cannula may be used for many purposes, such as, taking of blood samples, transfusion of blood, infusion of medications, and introduction of diagnostic or therapeutic apparatus. Early cannula were generally of a rigid metal design, for example, the hypodermic needle. Repeated puncturing of veins within a short period of time with such rigid catheters tended to cause venous thromboses and subcutaneous hematomas. This frequently occured during normal hospitalization. To reduce injury and prevent soreness, the practice was developed of implanting a single rigid cannula into the lumen and performing successive procedures through the single catheter. When such a rigid needle (as used herein needle will mean a rigid hypodermic needle) was implanted within the patient, the risk existed that the needle would move relative to the lumen, puncturing the vein causing additional injury. In order to prevent movement of the needle relative to the body, it was necessary that the portion of the body where the needle was inserted to be immobilized. This resulted in considerable discomfort and potential injury to the patient.
Recognizing the discomfort and risk of injury associated with permitting a needle to remain in the body for an extended period of time, it was appreciated that replacing the needle with a flexible catheter was more desirable. This solution required that a method for implantation of such catheters be developed. Two systems were developed for inserting such flexible catheters. These methods are commonly referred to as "through-the-needle" and "over-the-needle".
The first method, "through-the-needle", utilized a hollow rigid catheter, needle, through which a flexible catheter could be inserted. Once the flexible catheter was in place the needle was removed from the body. The catheters implanted by this method were necessarily small. These small diameter piable catheters were difficult to manipulate because they were subject to bending, folding, and tearing. In addition, great care had to be exercised when retracting the needle from the patient and catheter, not to dislodge the catheter. Later needles were designed to minimize this risk. These needles could be opened along their logitudinal axis after being withdrawn from the patient, allowing the flexible catheter inside to be easily removed, as disclosed in U.S. Pat. No. 3,359,978 issued to Smith on Dec. 26, 1960 and entitled "Guide Needle for Flexible Catheters". A major disadvantage of this method was that the catheter to be inserted through the needle was relatively small and difficult to insert.
A second type of flexible catheter insertion is generally referred to as "over-the-needle". In this method, the flexible catheter is telescopically mounted over the rigid needle. The needle is inserted into the vein and the flexible catheter is then slid into the vein. Once the flexible catheter is placed the rigid needle is withdrawn from the lumen and the catheter. The major difficulty encountered with this system was that the flexible catheter had to be semi-rigid in order to penetrate the tissue. Although such catheters were semi-rigid, they were more preferable than a needle because they were relatively blunt ended and posed less of an injury risk than the needle.
To address the shortcomings of the through-the-needle and the over-the-needle concepts a third approach was developed which combined the two steps. The first step was to insert a semi-rigid introducer catheter by the over-the-needle technique. Once the needle was withdrawn from the semi-rigid introducer catheter a pliant infusion catheter was inserted through the introducer catheter. Once the infusion catheter was in place, the introducer catheter could be removed from the body and from around the infusion catheter. This method permits the use or a larger infusion catheter which is less vulnerable to tearing, buckling, bending or kinking. As a result, it may be more easily and quickly implanted thereby reducing the risk of injury during implantation. This method has also found use in the implantation of other devices, for example, pacemaker leads. As used herein "primary device" refers to the device which is inserted through the introducer catheter recognizing that it may be an infusion catheter, diagnostic or therapeutic device.
The present invention relates to an improved introducer catheter assembly design and the provision of a sleeve which functions to prevent premature splitting of the introducer catheter and, also, as a site for suturing the primary device to the patient. Those skilled in the art will appreciate that the introducer catheter of the present invention is not restricted to implantation by means of a needle only, but may also be implanted within the patient by making an incision in the patient.